An Atlas booster with a Centaur upper stage, AC-5 was intended to carry a dynamic mass model of the Surveyor lunar lander into space. Due to a programming error, one of the booster's engines shut down immediately after lift-off causing the vehicle to fall back and resulting in the most powerful launch pad explosion in US space history. Scaled up, the effects of this blast were used to to model the consequences of a Saturn V explosion - which fortunately never occurred.